METHOD AND DEVICE FOR DETERMINING AERODYNAMIC CHARACTERISTICS OF AN AIRCRAFT

• US 20100222945A1
• Filed: 02/12/2010
• Published: 09/02/2010
• Est. Priority Date: 02/27/2009
• Status: Active Grant

• Current Assignee: Airbus Operations GmbH (Airbus SE)
• Original Assignee: Airbus Operations GmbH (Airbus SE)
• Inventors: Stegelmeier, Wilfried, Tauzin, Chloé, Giesseler, Hans-Gerd
• Granted Patent: US 8,442,705 B2
• Time in Patent Office: Days
• US Class Current: 701/14
• CPC Class Codes: G01M 9/06 Measuring arrangements specially adapted for aerodynamic testing

Abstract

The present invention provides a device and method for determining aerodynamic characteristics of an aircraft, in particular a pitch moment coefficient at an ascending force of the aircraft without a horizontal tail plane of zero and an aerodynamic neutral point of the aircraft without a horizontal tail plane. In the method according to the invention, forces and mechanical flight parameters on aerofoils and a horizontal tail plane of the aircraft are detected at various detection instants during at least one non-stationary flight manoeuvre of the aircraft. In this case, a linear system of equations is formed, which comprises a pitch movement moment balance equation for each detection instant, the pitch movement moment balance equation having the detected forces and mechanical flight parameters. This linear system of equations is evaluated to calculate the aerodynamic characteristics.

Claims

1. A method for determining aerodynamic characteristics of an aircraft comprising the steps:

(a) Detecting forces and mechanical flight parameters on aerofoils and a horizontal tail plane of the aircraft at various detection instants during at least one non-stationary flight manoeuvre of the aircraft; and

(b) Evaluation of a system of equations, which comprises, for each detection instant, a pitch movement moment balance equation, which has the detected forces and mechanical flight parameters, to calculate the aerodynamic characteristics of the aircraft.

2. The method according to claim 1, wherein by evaluating the system of equations, a pitch moment coefficient at an ascending force of the aircraft without a horizontal tail plane of zero and an aerodynamic neutral point of the aircraft without a horizontal tail plane are determined as the aerodynamic characteristics.

3. The method according to claim 1, wherein the evaluation of the system of equations on the basis of forces and mechanical flight parameters recorded during the flight manoeuvre takes place at a later instant or in real time.

4. The method according to claim 1, wherein the system of equations is formed by a linear system of equations, which is solved by an overdetermined numerical optimisation method.

5. The method according to claim 1, wherein the flight manoeuvre is primarily a longitudinal movement manoeuvre of the aircraft.

6. The method according to claim 1, wherein a spindle force in a trimming spindle of the horizontal tail plane and bearing forces in a left and right rotary bearing of the horizontal tail plane are detected by sensors during the flight manoeuvre.

7. The method according to claim 1, wherein a vertical load factor at the centre of gravity of the aircraft, a vertical load factor at a centre of gravity of a trimming tank and a vertical load factor at a centre of gravity of the horizontal tail plane are detected by sensors during the flight manoeuvre or derived from sensor data.

8. The method according to claim 6, wherein the vertical ascending force F_z^wfp of the aircraft without a horizontal tail plane is calculated as a function of the spindle forces and bearing forces of the horizontal tail plane detected by sensors and of the detected or derived vertical load factors by means of the following vertical load factor equation:

$-{\mathrm{mgn}}_z^{\mathrm{cg}}=F_z^{\mathrm{wfp}}+\frac{1}{\mathrm{co}}<br><br>\left[F_z^{\mathrm{screw}}+F_z^{\mathrm{attach}<br><br><br><br>L+R}-m^{\mathrm{HTP}}<br><br>{\mathrm{gn}}_z^{\mathrm{HTP}}-m^{\mathrm{TT}}<br><br>{\mathrm{gn}}_z^{\mathrm{TT}}\right]$

wherein co is a predetermined carry over factor,

g is the gravitational constant,

m is the mass of the aircraft,

m^HTP is the mass of the horizontal tail plane,

m^TT is the mass of the trimming tank,

n_z^cg is the vertical load factor at the centre of gravity of the aircraft,

n_z^HTP is the vertical load factor at the centre of gravity of the horizontal tail plane,

n_z^TT is the vertical load factor at the centre of gravity of the trimming tank,

F_z^screw is the spindle force in the trimming spindle of the horizontal tail plane,

F_z^{attach L+R} is the bearing forces in a left and right rotary bearing of the horizontal tail plane.

9. The method according to claim 8, wherein the pitch movement moment balance equation has the vertical ascending force F_z^wfp of the aircraft calculated by the vertical load factor equation, without a horizontal tail plane:

$\mathrm{qS}<br><br><br><br>1_{\mathrm{\mu <br><br>}}<br><br>C_{m<br><br><br><br>0}+F_z^{\mathrm{wfp}}<br><br>\frac{1<br><br><br><br>\mathrm{\mu <br><br>}}{100}<br><br>h_0={\left(I<br><br><br><br>\stackrel{·<br><br>}{\stackrel{-><br><br>}{\mathrm{\omega <br><br>}}}\right)}_y+{\left(\stackrel{-><br><br>}{\mathrm{\omega <br><br>}}<br><br><br><br>x<br><br><br><br>I<br><br>\stackrel{-><br><br>}{\mathrm{\omega <br><br>}}\right)}_y-\mathrm{qS}<br><br><br><br>1_{\mathrm{drag}}<br><br>C_x+F_z^{\mathrm{wfp}}<br><br>h<br><br>\frac{1<br><br><br><br>\mathrm{\mu <br><br>}}{100}-\frac{1}{\mathrm{co}}<br><br>\left[F_z^{\mathrm{screw}}<br><br>1^{\mathrm{screw}}+F_z^{\mathrm{attach}<br><br><br><br>L+R}<br><br>1^{\mathrm{attach}}-m^{\mathrm{HTP}}<br><br>{\mathrm{gn}}_z^{\mathrm{HTP}}<br><br>1^{\mathrm{HTP}}+m^{\mathrm{TT}}<br><br>{\mathrm{gn}}_z^{\mathrm{TT}}<br><br>1^{\mathrm{TT}}\right]-T_{\mathrm{outer}}<br><br>1^{\mathrm{outer}}-T_{\mathrm{inner}}<br><br>1^{\mathrm{inner}}-\mathrm{qS}<br><br><br><br>1_{\mathrm{\mu <br><br>}}<br><br>\frac{\partial <br><br>C_m}{\partial <br><br>n_z}<br><br>n_z^{\mathrm{cg}}-I_{\mathrm{yy}}^{\mathrm{HTP}+\mathrm{TT}}<br><br>{\stackrel{.}{\mathrm{\omega <br><br>}}}_y$

wherein

ω

=rotation rate of the aircraft,

q is the occurring back pressure,

S is the area of an aerofoil of the aircraft,

l_μ

is the aerodynamic wing depth of the aerofoil,

h₀ is the aerodynamic neutral point of the aircraft without a horizontal tail plane,

T_outer is the thrust of the outer engines mounted on the aerofoil,

T_inner is the thrust of the inner engines mounted on the aerofoil,

C_x is the coefficient of aerodynamic force,

l^drag, l^screw, l^attach, l^HTP, l^TT, l^outer, l^inner are the lever arm lengths for the air drag, the trimming spindle loads, the rotary bearing loads, the inertial force of the horizontal tail plane HTP, the inertial force of the trimming tank TT, the thrust of the outer engines and the thrust of the inner engines.

10. The method according to claim 9, wherein the overdetermined linear system of equations formed from pitch movement moment balance equations for m detection instants:

$\left[\begin{array}{cc}\mathrm{qS}<br><br><br><br>1_{\mathrm{\mu <br><br>}}<br><br>\left(1\right)& F_z^{\mathrm{wfp}}<br><br>\frac{1_{\mathrm{\mu <br><br>}}}{100}<br><br>\left(1\right)\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ \mathrm{⋮<br><br>}& \mathrm{⋮<br><br>}\\ \mathrm{qS}<br><br><br><br>1_{\mathrm{\mu <br><br>}}<br><br>\left(m\right)& F_z^{\mathrm{wfp}}<br><br>\frac{1_{\mathrm{\mu <br><br>}}}{100}<br><br>\left(m\right)\end{array}\right]<br><br>\left[\begin{array}{c}{C}_{m<br><br><br><br>0}\\ h_0\end{array}\right]=\left[\begin{array}{c}b<br><br>\left(1\right)\\ \mathrm{⋮<br><br>}\\ \mathrm{⋮<br><br>}\\ \mathrm{⋮<br><br>}\\ b<br><br>\left(m\right)\end{array}\right]$

is solved according to the pitch moment coefficient and the aerodynamic neutral point of the aircraft without a horizontal tail plane, wherein b is the inhomogeneity of the overdetermined linear system of equations.

14. A programme with programme commands for carrying out the method according to claim 1.

15. A data carrier which stores the programme according to claim 14.

11. A device for determining aerodynamic characteristics of an aircraft comprising:

(a) Sensors for detecting forces and mechanical flight parameters on aerofoils and a horizontal tail plane of the aircraft at various detection instants during at least one non-stationary flight manoeuvre of the aircraft; and

comprising

(b) A calculation unit to evaluate a system of equations, which for each detection instant comprises a pitch movement moment balance equation, which has the detected forces and mechanical flight parameters to calculate the aerodynamic characteristics of the aircraft.

12. The device according to claim 11, wherein the device is mounted on the aircraft.

13. The device according to claim 11, wherein the sensors are mounted on the aircraft and transmit the detected forces and mechanical flight parameters via a radio interface to a base station having the calculation unit.